1. Field of the invention
The present invention relates to a joining jig for coupling joining members that join a plurality of workpieces, such as panels, and also to a joining member coupling method using the jig.
2. Description of the Related Art
In a conventional method for joining body panels of an automotive vehicle, plastically deformable sleeves are used as bolt fixing members similar to nuts, by disposing a sleeve onto a bolt shaft and deforming and tightening it to the bolt shaft. FIG. 29 illustrates such a method, where a sleeve 102 is to be deformed and tightened to a bolt shaft 101.
The bolt shaft 101 is welded to a workpiece W.sub.1. The sleeve 102 has a flange 103, a tool engaging portion 104 and a barrel portion 105. The inside diameter of the sleeve 102 is greater than the diameter or the bolt shaft 101 before the sleeve 102 is deformed for tightening. The tool engaging portion 104 has a hexagonal shape viewed from above, making it easy to engage and turn a wrench or the like therewith for loosening when the sleeve 102 needs to be removed after it has been tightened. The barrel portion 105, having a generally circular shape, is the part to be deformed by the tightening operation.
To join workpieces, the bolt shaft 101 is first inserted into the hole of a workpiece W.sub.2 and the sleeve 102 is loosely fitted onto the bolt shaft 101. Then, a nose 107 of a tool 106 is set over the bolt shaft 101 so that a clamp 108 of the tool 106 holds the bolt shaft 101. By pulling the clamp 108 up, the reaction force presses the nose 107 against the barrel portion 105 of the sleeve 102. The barrel portion 105 is thereby deformed by the nose 107 so as to reduce the inside diameter of the sleeve 102. The sleeve 102 is thus tightly fastened to the bolt shaft 101. Since the thread of the bolt shaft 101 is impressed onto the inside peripheral wall face of the sleeve 102, this method achieves a significantly tight attachment and restrains loosening of the bolt more effectively than a method using an ordinary bolt and nut. A conventional method using sleeves as mentioned above is disclosed in detail in WO 94/01687.
However, the above-described conventional art has the following drawbacks. For tightening the sleeve 102, the clamp 108 holding the bolt shaft 101 is pulled out so that the reaction force presses the nose 107 against the sleeve 102. Since the pulling force is directly applied to the bolt shaft 101, the tightening force, which depends on the pulling force, is limited within a range allowed by the strength of the bolt shaft 101. Moreover, if this sleeve tightening operation is to be performed simultaneously on a plurality of bolt shafts, it becomes necessary to provide a plurality of noses 107 each of which has a clamp 108 provided therein and a drive mechanism for the clamp 108, thus complicating apparatus construction. Furthermore, since the tightening force must be controlled corresponding to the strength of each bolt shaft 101, the simultaneous tightening operation on a plurality of bolt shafts requires a complicated control system. Therefore, it is normal practice to perform the tightening operation on one bolt at a time.
Another conventional tightening method is proposed, as illustrated in FIG. 30. In this method, a bolt shaft 110 is positioned by using a stopper 109, and then workpieces W.sub.1, W.sub.2 and a sleeve 111 are fitted onto the bolt shaft 110. The conical inner wall surface 113 of a tool 112 is pressed against a conical tightening portion 114 of the sleeve 111 to simply compresses the sleeves 111. However, since the sleeve 111 is fastened by pushing the tool 112 so that the thrust is transmitted from the inner wall surface 113 to the tightening portion 114 of the sleeve 111, there is a likelihood that a force unsuitable in magnitude or direction will be applied to the bolt shaft 110, thus bending the bolt shaft 110. Therefore, it is required that the length of the bolt shaft 110 be limited and the sleeve 111 be low and wide in shape, and such requirements impose limitations on where these joining members can be used.